Set of non-duplicate items for CosmWasm smart contract store.
In this example, we create a whitelist of users. This may be useful in, for example, NFT minting whitelists.
```rust use cosmwasmstd::{DepsMut, Order, StdResult}; use cwitem_set::Set;
// "whitelist": namespace under which the items are to be stored // "whitelistcounter": key for storing the total number of items in the set const WHITELIST: Set<&str> = Set::new("whitelist", "whitelistcounter");
fn example(deps: DepsMut) -> StdResult<()> { // Add a new user to the whitelist WHITELIST.insert(deps.storage, "larry")?;
// Remove a user from the whitelist
// Note that we don't check whether the user already exists in the whitelist.
// Attempting to remove a non-existent user won't result in error.
WHITELIST.remove(deps.storage, "jake")?;
// Check whether a user is in the whitelist
let is_whitelisted = WHITELIST.contains(deps.as_ref().storage, "pumpkin");
// Check the total number of users in the whitelist
let num_users = WHITELIST.count(deps.as_ref().storage)?;
// Enumerate all users in the whitelist
for res in WHITELIST.items(deps.as_ref().storage, None, None, Order::Ascending) {
let user = res?;
println!("{} is whitelisted!", user);
}
// Delete all users in the whitelist
WHITELIST.clear(deps.storage);
Ok(())
} ```
There are two optional features, both enabled by default:
iterator: The range, prefix, and clear functions require this feature.
counter: The count function requires this feature. If enabled, an Item<u64> will be created to store the total number of items in the set. In this case, it is necessary to provide a storage key for the counter when declaring a set:
``rust
//counter` feature ENABLED
// The new function takes two parameters, the namespace for the set, and the
// key for the counter.
const WHITELIST: Set<&str> = Set::new("whitelist", "whitelist__counter");
// Use the count function to get the total number of items in the set.
let num_users = WHITELIST.count(deps.storage)?;
```
If counting the total number of items in the set is not needed, it is recommended to disable this feature, which saves gas by avoiding having to update the counter every time an item is added or removed.
In this case, the store key parameter is no longer needed when creating a set.
``rust
//counter` feature DISABLED
// Only the set namespace is required const WHITELIST: Set<&str> = Set::new("whitelist");
// This won't compile: count function is not supported
let num_users = WHITELIST.count(deps.storage)?; // ERROR!
```
Contents of this crate at or prior to version 0.7.0 are published under GNU Affero General Public License v3 or later; contents after the said version are published under Apache-2.0 license.